One type of medical instrument that is steered through body passages is an endoscope. Endoscopes allow physicians to capture images of and diagnose problems with internal body organs by inserting the device either through a natural orifice or a surgeon created opening and guiding it to a target site within a patient. In some cases, it may also be used to perform medical procedures on the internal body organs. It may be steerable so that its distal tip is controllably oriented for navigation purposes. An image capturing device such as a stereoscopic or monoscopic camera may be provided at its distal tip so that images captured by the camera from that perspective may be viewed on a display screen by the surgeon. To perform various medical procedures at the target site, surgical tools, such as those used for cutting, grasping, cauterizing, etc., may extend out of the endoscope's distal tip.
Specialized endoscopes may be named for where they are generally intended to look. Examples include: cystoscopes for looking in the bladder, nephroscopes for looking in the kidney, bronchoscopes for looking in bronchi of the lung, laryngoscopes for looking in the larynx, otoscopes for looking in the ear, arthroscopes for looking at joints, laparoscopes for looking inside the abdomen, and gastrointestinal endoscopes. In order to look at their intended organs, endoscopes may move through linked body passages in the body to a target area.
Another type of medical instrument that is steerable through body passages is a catheter. Catheters are long slender flexible tubes that are inserted into a natural bodily cavity or passage for introducing or withdrawing fluid. Its uses include the drainage of urine from the bladder through the urethra or insertion through a blood vessel into the heart for diagnostic purposes. Catheters may also be inserted in a passage to keep the passage open.
Still other types of medical instruments that are steerable through body passages are surgical and diagnostic tools. Examples include such common medical implements as forceps for taking tissue samples and electrodes used for cauterization of tissue.
Body passages through which such medical instruments are steered may be circuitous and have varying widths along their lengths. Further, they may be multi-branched and narrow so that navigation to target areas in the body is difficult. Also, the passage may comprise sensitive tissue that is easily harmed by excessive physical contact with the medical instrument. As an example of linked body passages, U.S. Pat. No. 7,901,348 B2 describes visual-assisted guidance of an ultra-thin flexible endoscope to a predetermined region of interest within the bronchial tree of a lung during a bronchoscopy procedure. As other examples of linked body passages, U.S. 2005/0182319 A1 describes image guided surgery techniques applicable to the blood circulatory system as well as the air circulatory system of the lung, the digestive system, and the urinary system.
When an operator is inserting a medical instrument through linked body passages to a target area in an anatomical structure of a patient, it may be desirable to assist the operator in navigating the medical instrument to the target area. In retracting the medical instrument back out of the linked body passages, care must be taken to avoid harming the passage walls by excessive physical contact with the medical instrument. Safety for the patient is a primary concern at all times while controlling movement of the medical instrument in the patient.